The present invention relates to a process for producing mixtures enriched with 6-0-xcex1-D-Glucopyranosyl-D-sorbite (hereinafter, 1,6-GPS) and/or 1-0-xcex1-D-Glucopyranosyl-D-mannite (hereinafter, 1,1-GPM) from hydrogenated isomaltulose or from mixtures containing hydrogenated isomaltulose.
Hydrogenated isomaltulose is an almost equimolar mixture of 1,6-GPS and 1,1-GPM and is a commercially available sugar substitute. Its acariogenicity, low calorie content, and suitability for diabetics provide substantial benefits. Pure 1,6-GPS and 1,1-GPM or mixtures containing larger amounts of 1,6-GPS and 1,1-GPM can be advantageously used in a number of applications, such as, for example, in the food industry, where these solutions are superior to products containing equimolar ratios of 1,1-GPM/1,6-GPS. However, manufacturing processes for producing mixtures enriched with 1,6-GPS or 1,1-GPM or pure 1,6-GPS and 1,1-GPM which enable a simple and efficient production from a readily available starting material, are not known to date.
It is therefore an object of the invention to provide a suitable manufacturing process for producing large quantities of pure 1,1-GPM and 1,6-GPS as well as mixtures of 1,1-GPM. and 1,6-GPS with a high yield.
The object is achieved by the process for producing mixtures enriched with 1,1-GPM and 1,6-GPS as well as pure 1,6-GPS and pure 1,1-GPM, which comprises:
(i) dissolving hydrogenated isomaltulose or a mixture containing hydrogenated isomaltulose in water at an elevated temperature;
(ii) subjecting the solution produced in step (i) to one or more cooling steps to produce distinct phases enriched in 1,1-GPM or 1,6-GPS, wherein each cooling step comprises cooling the solution at a predetermined rate over a predetermined temperature range; and
(iii) separating the phase enriched with 1,1-GPM from the phase enriched with 1,6-GPS.
The phases enriched with 1,1-GPM or 1,6-GPS are produced with the process of the invention by dissolving hydrogenated isomaltulose or a mixture containing hydrogenated isomaltulose in water at elevated temperatures and cooling the solution over a predetermined temperature range to crystallize the solution and to obtain the desired phase composition. The 1,1-GPM-rich phase is subsequently separated from the 1,6-GPS-rich phase, preferably by centrifugation. The cooling process for the crystallization can be either discontinuous or continuous.
In a preferred embodiment, the solution is cooled to crystallize in a temperature range from about 90xc2x0 C. to about 65xc2x0 C. at a cooling rate of 5 to 15 K/h and in a temperature range from about 75xc2x0 C. to 37xc2x0 C., in particular 65xc2x0 C. to 37xc2x0 C., at a cooling rate of 0.4 to 10 K/h, preferably of 0.4 to 3 K/h.
In the context of the present invention, hydrogenated isomaltulose is defined as an equimolar or almost equimolar mixture of 1,1-GPM and 1,6-GPS. A mixture containing hydrogenated isomaltulose is defined as a mixture of 1,1-GPM, 1,6-GPS as well as of one or more substances, including without limitation mannite, sorbite, saccharose, 1,1-GPS (1-0-xcex1-D-Glucopyranosyl-D-sorbite), isomaltose, hydrogenated or unhydrogenated oligosaccharides, isomelezitose, or other substances. Suitable starting materials for the process of the invention are, for example, the sweeteners described in EP 0 625 578 B1.
Within the framework of the present invention, a temperature is defined as elevated if the hydrogenated isomaltulose or the mixture containing the hydrogenated isomaltulose can be completely or almost completely dissolved in water, provided that the prescribed starting concentration is used in the cooling crystallization, for example 70 to 90 wt. % solid phase content.